Time delay relay



June9, 1942. YER 2,285,677

TIME DELAY RELAY Filed Dec. 28, 1939 To Contra! Gz'r'am't.

WITNESSES: INVENTOR zfln. Julz'zzsfl Myers.

I BY add/m I v W Patented June 9, 1942 TIME DELAY RELAY Julius D. Myers, Scotch Plains, N. J., assignor to Westinghouse Electric Elevator Company, Jersey City, N. J., a corporation of Illinois Application December 28, 1939, Serial No. 311,395

7 Claims.

My invention relates to a time delay relay and more particularly to a time delay relay of the type employing a temperature responsive member, as, for example, a bimetallic element.

It is an object of my invention to provide a novel relay which utilizes the cooling period of a thermostat to make possible improved accuracy in selecting the period of time delay.

It is another object of my invention to provide such a time delay relay which is novel and economical and may be readily reset after an operation.

Another object of my invention is to provide a novel relay which will supply a plurality of different time delays.

According to one form of my invention, a resistance coil is disposed in heating relationship to a bimetal fixed at one end. The other end of the bimetal is arranged to move as it is heated until a contact carried thereby and connected to an end of the heating coil engages a stationary contact connected to the other end of the heating coil to shunt it. While the heater is shunted, the bimetal cools to a point at which the shunt circuit is disengaged, whereupon the heater again functions. Thus the bimetal is retained at a substantially constant temperature, and upon the energy source being disconnected from the heating coil, it cools and, in a predetermined time,

carries a contact bridging member disposed on its movable end to a position closing an operating circuit. A plurality of these units, each adjusted to have a different cooling period, may be employed to operate each of a plurality of circuitsafter diflferent time delays.

Other objects of my invention will become evident from the following detailed description,

taken in conjunction with the accompanyingdrawing, in which:

Figure 1 shows a preferred form of my invention partly in perspective; and

Fig, 2 is a schematic showing of another form of my invention.

Referring to Fig. 1, a pair of bimetal elements "I and 2 are each secured at one end to a support 3 by meansv of a conducting plate 4 attached thereto as by bolts 5. On the other or movable ends of the bim'etals I and 2 are disposed bridging conductors 6 and I, respectively, which are insulated from the bimetals by blocks 8 and 9 of non-conductive material. Contacts I0 and II are disposed on the upper portions of the bimetals I and 2, respectively. Arranged to be engaged by these contacts when the respective bimetals ar in predetermined heated conditions are stationary contacts I2 and I3, which may be made adjustable in any suitable manner, as by the screw and nut arrangement shown.

A resistance-type heater I4 is coiled around the bimetal and connected at one end to the contact I0, while a similar heating coil I5 is connected at one end to the contact II and arranged to heat the bimetal 2. The stationary ends of both bimetals are connected through a switch IE to one terminal I! of an electrical energy source, which may supply either direct or alternating current. The ends of the heating coils I4 and I5 not connected to their corresponding bimetals-are connected through limiting resistances I8 and I9, respectively, to the other terminal 20 of the energy source. Shunt circuits 2i and 22 are each connected between a resistance and the corresponding heating coil and to one of the stationary contacts I2 and I3, respectively.

A pair of contacts 23 are arranged tobe closed by the bridging conductor 6, and another pair of contacts 24 are adapted to be interconnected by the bridging member I when the respective bimetals are at a temperature slightly above ambient.

It will be evident that with the switch It closed the heating coil I A will be energized through the following circuit: terminal I'I, switch I6, conducting plate 4, bimetal I, contact III, heating coil I4, resistance I8, and terminal 20. Upon the bimetal being heated to a predetermined temperature, it will be flexed to the position where the contact I0 engages stationary contact I2, thus shorting the heater I4 and permitting the bimetal to cool. After cooling a small amount, the bimetal I disengages the contacts I0 and I2 and again places the heater I4 in operation. This cycle continues, thus retaining the bimetal I at a substantially constant temperature and deformation. The bimetal 2 is retained in a similar condition by means of its heating circuit.

Upon the switch I6 being opened, both bimetals are permitted to cool and after a predetermined time the bimetal I places its bridging conductor 6 in position, interconnecting the contacts 23. The bimetal 2, having a longer cooling period than the bimetal I, either because of the selection of elements having different inherent temperature characteristics, as a result of ditlerent adjustments of the stationary contacts I2 and I3 or both, acts to interconnect contacts 23 after a longer period of time. Thus, as has been found useful in electric elevator signalling systems, contacts 23 may be closed after approximately ten seconds delay, and contacts 24 after approximately twenty seconds. Preferably, the bridging members close their corresponding contacts before the bimetals return to normal cooled position so as to create a contact pressure.

The purpose of the external or limiting resistances l8 and I9 is to prevent a short on the energy supply when either, or both, ofthe heating coils l4 and I5 is in shunted condition.

In Fig. 2, which shows schematically a relay in accordance with my invention employing a single bimetal, primed numerals are utilized to designate elements corresponding to those in the circuit of the bimetal l in Fi 1.

In this arrangement of Fig. 2, a bimetal I is supported by one end at 3, while the other end has disposed on its upper side a contact l0 and on its lower side a bridging conductor 6. bridging conductor is insulated from the bimetal l' by a block 8' of non-conductive material and is arranged to bridge contacts 23 when the bimetal is in cooled or substantially straight position.

One end of a heating coil H is connected to the contact III, which in turn is electrically connected to the terminal ll of an electrical energy source through the bimetal I and switch [6. The other end of the heating coil i connected to the other energy supply terminal 20 through a limiting resistance I8. A shunt circuit 2| connects the heater coil Id at a point between the heater l4 and the resistance Hi to a stationary contact l2. Y

It will be obvious that this relay, which Fig. 2 shows in energized or circuit closing position, operates to give a single delay in the same manner as the apparatus of Fig. 1 furnishes two delay periods.

From the above description of my invention, many of itsadvantages will become evident. Because of the shunting arrangement, the heating element may be energized to an extent which would ordinarily heat the thermal element far above the desired maximum temperature, making available extremely rapid resetting characteristics. Using the cooling cycle for the time control also renders the ambient temperature over the normal ranges met in practice of small importance in affecting the time.

I do not wish to be restricted to the specific structural details, arrangement of parts, or circuit connections herein set forth, as various other modifications thereof may be effected without departing from the spirit and scope of my invention. I desire, therefore, that only such limitations shall be imposed as are indicated in the appended claims.

I claim as my invention:

1. A time delay relay comprising a thermostatic element carrying circuit operating means arranged to close a controlled circuit when said element is in a cool position, a separate electric circuit including a heater unit in heat conducting relationship to said thermostatic element to retain it in deformed condition with its circuit operating means in open circuit position, said heating circuit including means for shunting said heater unit when said thermostatic element is in a predetermined position of maximum deformation to maintain it at a substantially con stant temperature, and means for interrupting said heater circuit to return said thermostaticv element to saidcool position in a predetermined time to bring said circuit operating means to circuit closing position.

This

2. A time delay relay comprising a thermal element fixed to supporting means at one end and free to move at the other end in response to temperature changes, an electric circuit including a heater unit operatively associated with said thermal element, said heater circuit including a low resistance circuit arranged to shunt at least a portion of said electric heater when said thermal element is heated to a predetermined maximum temperature to maintain it within a predetermined small range of temperatures just below said maximum, means controlled by said thermal element to place a controlled circuit in a first condition when said thermal element is at a temperature exceeding a second predetermined temperature below said temperature range and in a second condition when said thermal element is at a temperature notexceeding said second predetermined temperature, and means to deenergize said electric heater to permit said thermal element to cool to said second predetermined temperature to changesaid controlled circuit from said first condition to said second condition after a predetermined time delay.

3. A time delay relay comprising a thermal element fixed to supporting means at one end and free to move at 'the other end in response to temperature changes, an electric heater operatively associated with said thermal element and arranged to be connected across an electrical energy source, one end of said heater being connected to the movable end of said thermal element, a stationary contact, a low resistance circuit connecting'said stationary contact to the end of said heater not connected to said thermal element, said stationary contact being arranged to engage the movable end of said thermal element when in a predetermined position of maximum deformation to shunt said heater with said low resistance circuit to maintain said thermal element at a substantially constant predetermined temperature, means controlled by said thermal element to place a controlled circuit in a first condition when said thermal element exceeds a predetermined lower temperature and in a second condition when said thermal element 1 does not exceed said predetermined lower temperature, and means to disconnect said heater from said energy source to permit said thermal element to cool to said predetermined temperature to change said controlled circuit from said first condition to said second condition after a.

predetermined time delay.

4. In combination, a circuit to be controlled, a device movable in response to temperature changes, means operable to change said controlled circuit from a first condition to a second condition upon said device cooling to a predetermined critical temperature, a heating circuit for normally maintaining said device at a substantially constant predetermined temperature in excess of said critical temperature, and means op erable to reduce the effect of said heating circuit to permit said temperature responsive device to cool to said critical temperature.

5. In combination, a circuit to be controlled, a device movable in response to temperature changes, means operable to change said controlled circuit from a first condition to asecond condition upon said device cooling to a predetermined critical temperature, an electric heater disposed in heat conducting relationship to said device, a circuit for energizing said heater to deform said device, said last named circuit including a portion operable to reduce the heating effect of said heater while said device is in a predetermined position of maximum defamation to permit cooling thereof and normally maintain said device at a substantially constant temperature in excess of said critical temperature, and means operable to interrupt the heater energizing circuit to permit said temperature responsive device to cool to said critical temperature.

6. In combination, a circuit to be controlled, a

thermostatic member movable in response to temperature changes, means operable to change said controlled circuit from a first condition to a second condition upon said member cooling to a predetermined critical temperature, an electric heater disposed in heat conducting relationship to said thermostatic member, a circuit for energizing said heater to deform said member, means in said energizing circuit for shunting at least a portion 01' said heater when said thermostatic member is in a predetermined position 01 maximum deformation to normally maintain it at a predetermined temperature in excess of said crittcal temperature, and means operable to reduce the heating effect c! said heater to permit said er to deform said member, means connected to said energizing circuit for shunting at least a portion of said heater when said thermostatic member is in a predetermined deformed position to limit its maximum deformation and normally maintain it in a predetermined deformed condition corresponding to a predetermined temperature in excess of said critical temperature, and means operable to interrupt said heating circuit to permit said thermostatic member to cool to said critical temperature.

JULIUS D. MYERS. 

